Sizing bridge



July 27, 1948. Q HURLEY JR M 2,446,046.

y SIZING BRIDGE Filea'spt. 2:5, 1944 l INVEN TOR. S. C. Hum 5y J.

BYBM' wct' fmtmvab Patented July 27, 1948 PATENT uor1=fuzzt,

-`2,446,046 `sxzma namen:

` samuelfcrnurlea Jr.,-Danviue;m.lApplicationiseptemberzsfiemfserial10:55am

` t llaims. l tl t'fflhisptinventionf relatestozthe improvedwmethodfandiapparatus V.forrpllotoelectricffinspectionu:or lar- "ticles :of:manufacture and particularly 1@,.to sa :methodffan'd apparatus,aforfzemaking. `precision ldit:mensionalmeasurements. t

LThiszapplicationvista continuation ina-part of irny:copendingapplication' for 480,025r'1ed March 22, 1943, now abandoned, which, in`turngissarcontinuation in partfsof :my abandonediapplication3473,187g1r1ed January1.22,:1f943.

.Itflparticularly relateszltoa methodzfandrapparatus' for 1 using i abridge circuit for :selecting "for l `:rej ectingrarticles lof:lmanufacturea in A:,iaccordance to the predetermined dirnensonfof: thearticle; and specicallyi to? vafixievice fand: method wherein flthe.selecting-tor. rejectngimechanismfcan befmade to function :sharply v.at 's each textr'emity il of .a the adgfjustable :tolerance frange. l

I`I-My inventionv ffembodies -a novel zmethod and tapparatusnlin`Which'la bridgev lcircuitriconta'ining light @sensitive devices`forfmakingia jphotolectric inspectionts/hereinthe; results! of ,thisinspection -v-mayl libe' quickly; \facourately..andfi readily iobtained.The bridge circuitisconnectedlin aemanner 4that the desired inspectionisi-onlylindicated'i foru one 1 state ofl unbalance of thebridgelcircit,Vand any other state of `1un'lo'ala'nce' oril1 a"fba1ancedstate lwill Iindicate the'fundesiredinspection.

VlMyinvention isuseful inthe sizingfofarticles,

Wherever rapid-precisionphotoelectrical inspeclfterrnininglWhether-aniarticle-isfofA aiL predeter- 'Jmine'd szelf although' itmayI -be used f in'determin- Fing and# sorting articles of-f-di'lerentfsizes.

" It isialsouseful infconnection with photoelect'tricinspectionswhereinfail mechanical=-stops-and` reference points arereplaced by photoelect'ric means wherein eachcontrol grid; contrlli'ngthe ow-i of =cur-rent throughl anelectronic circuit; is controlled by my'bridge circuit.V

It fis-'one'. "object: lofniyi'invention"td-provide a novel bridgecircuit which will actuate an energy `'translation' meansusedininterpre'tingrthe resuit of the inspection; wherein the translation*means* is only actuated "when"thefbrldgefis .un-

It is another object of my inventioni'twprovide af`sing1eamplifyingrstage'inconne'ctionf'\with the ,l

f bridge circuit yf"irh'ereinthe energy Vtranslation -"-means `'isactuatedonlyWhenvfthe-bridge #is funbalancedin a positive directionprepotential,

It Lis 'also-f anI` object Lfemy finvention-to'provide (Clgl250-J-415)L2 al two stage-amplifying: system t in r eonnectionrwith :.myibridgecircuiti whichy is t particularlytusweful in .glphotcelectricalcamminglfwherein the energy `-ftranslation.-irneans `:is actuated `only when:the 5 sbridge vis unbalanced 'inh a megative directionzof potentiai t AIt "is :ai `further objectaof my inventiontorprowidexa :plurality-lorphototubesconnectedffin each side'of'thetbridge wherein the vtubesareconnected .inseriesinfone side; of the :bridge and inparallel v:in thefather iside of thefbridge. Thisv typeffof bridge circuit @beingparticularly- -usei'ul inconcxnection `with J making two or f moretdimensional iiinspections :of :them article although-,it hasvgmany l 5t'fotherrapplications y Another object of vmy` invention Vvis to provideE: in combination With-my bridge circuit; a novel `optical systeminwhichlthe :maximum and minirrrum tolerance lmayxbeuindependently :variedbyinderpendently cha'ngingtheA position'fof `the'lightfsensitivedevicetused f in the photcelectricg-inspection @aboutazrnagnifying mirror positioned lto receive z.-lightz;passing :ith-rough.fthe inspection zone. t

"Itfis1also .anobject off my: invention r tuv provide :iatselectingsmechanism for: accepting fand rejecting an earticles'iithichnormally is connected-1in rsuchamanner thatr it willfreject thearticleland nthezarticlewilbbeacceptedgonly byupositive actionmtxmyacircuit. ,Thisz prevents the operationlof-the1:.iaccepting'mechanism :in vcase a :portionrof the rcirarcuit .shouldfail,V ;e..\fg.,;one;of1the amplifyingttubes burneout.y'Ihisz'isr-high'lyV importantinI precisionl\dimensional'znea'surement,fwherein it is essential 1i tof-:prevent:,:a abad I specimen Vfrom :being:v passed .-along: withi atgood`specimen. J 4It :wouldrminimize tithe cadvantages of .:my t device if.the selecting `fmeehanisrrnwereg,ar -anged to: normally accepta theA:article land onlyf rejecty theaarti'cle ii'L-some-:positiveiractiomoccurred. Im-this case,V if anyfpart othemasi/stem"failedzitrmightrpass a number ofrbadapieces along With thegood pieceslbefore" t-heNfailurecould che; discovered.Thisisrparticularly harmfulfwhen s tithe-:apparatus is .used f toinspect articles land meqiiipnientirforluse in vconnection withsmachinesyinherently: :dangerous :such-"as: autornobiles, tacro-:,p1anes,'1:rnany :types 'ofi industrial= l 'equipmentnmazrchineslanidammunition for war Where it: isizthe utmost importance rthat; all'fthe ."articles, Lspecifamensglpartsy etc., :ltllat `are 'zaccepted`then-Linspection device becusdswith condencefandsthat etheyr: meet"lthev xcaretulsconsidered predetermined f requirements.vn'Itisvtal'thatlall of the inspected articles tare goodl because-1 the'use of 1 a single bad apiece mightrresultl iny I.severe property`damageiif b-notthelloss of; life. fItxis: Lparticularlyimportant -theprinciples o'f my device.

matching colors, comparison of reflected light,A

determination of light intensities, etc., but rhave been used whereinthe bridge is in balance -to indicate the desired result of theinspection. But bridge circuits of any kind have not been used inprecision dimensional inspections'. "The bridge f circuits heretoforeused would not be suitable for rapidly and accurately making precision"dimensional inspections. I accomplish this by f using a bridge in whichthe desired results of the j inspection are indicated only when thebridge'is unbalanced in one direction of potential and are lnotindicated when the bridge is in balance or when the bridge isunbalancedin the direction of potential opposite to the direction of unbal- "anceVfor indicating the desired results of the inspection. Using a balancedcondition of the bridge to accept the article would not be operative' inprecision dimensional inspections and using the bridge circuit toactuate the reject mechanisms would not be suitable. In my de- 'vice, itwould also be undesirable vto use the amplifier to measure the amount ofcurrent owing across the bridge and, on the contrary,

I` `provide a novel bridge circuit and optical y,

`system wherein the difference between a bad piece and a good piecewithin the tolerance range is sharply defined in order to preventinaccuracies.

AGradations from good to bad cannot be used but all-lof these objectivescan be obtained by using The current flowing through the amplifying tubepreferably goes from a maximum to a minimum or from a minimum to amaximum depending on conditions of light l'and Lshadow on the lightsensitive devices. 'NPhotoelectric circuits independently operated fhavebeen used to make dimensional inspections but are not suitable for usein high precision, rapid, dimensional measurements for which my deviceand apparatus is particularly suited, since thek previous devices `usedcomplicated relay systems for obtaining a co-action between the cir- Ycuits and for actuating the final selecting means. a Mechanicalswitchesand relay switches are urldesirable since they lag behind thephotoelectriol `inspection and minimize theadvantages obtained byphotoelectric inspection. By my device, I am able to make severalhundred inspections per l `minute which would be impossible to make withv'complicated relay systems.

. In general, my device comprises means for pro- 'jecting'a beam oflight through an inspection zone, means for positioning the article tovbe inspected in the inspectionzone, and means for determining theinspection desired when the 1 bridge is unbalanced in one direction ofypotential only, and 'means for determining thatthe article |-didnct meetthe required test byV determining any 1 other condition of the bridge. yIn a more specic embodiment, I provide an. f energytranslation meanswhich may actuate a lselecting mechanism` and which is controlled by asingle amplication stage, 'said amplifying stage fresponsive; only whenVthe bridge is unbalanced in a positive direction which means that insizing amebic tion, Iy employ a two-stagenampliication system for4actuating the energy translation means wherein the first stage of"amplification is controlled such as to actuate the energy translationmeans only when the bridge is unbalanced in a negative direction whichmeans that the light sensitive device or devices which must be in lightn' when'the desired inspection is obtained are locatedin theY negativearm of the bridge and the lightsensitive device or devices which must bein shadow when the desired inspection is obtained vare located in thepositive arm of the bridge.

The rst stage of amplification is actuated and the second stage is notactuated when the desired inspectionis obtained. To prevent theoperation of the selecting mechanism for accepting' the said `'articlein case the first stage amplifier burns out, I provide a means yforpreventing vthe operation of the second stagewhich would otherwise beactuated.

In another specic embodiment of my invention, I provide a means `forVsimultaneously making two or more inspections of the article, in

which case I connect allV the light sensitive devices Which must beV inlight fora good piece, in series in one arm of the bridge and thosewhich must be in shadow for a good piece in' parallel in the other armof the bridge, in which 'arm of the bridge Iplace the phototubesconnected 'in a series and those connected parallel depending uponwhether I use one or two stage amplification. B-y this novel means; allthe tubes ,whichmust be in light for goodpieces are'connected inseriesso that if any one of those are in shadow, it will unbalance'thebridgein the wrongdirection of potential for acceptingthearticle.

In anotherY embodimentV of my invention, I employ my lbridge circuit incombination'with a novel opticalV system wherein-the maximum tolerancemay beindependently adjusted by independently varying the position ofthe light vsensitive devices in the optical system;

Further-objects,^'uses and advantages of my invention will becomeapparent by referring `to the drawing inwhich Figurev lillustrates thearticle. -1

optical system which may be used in connection with my bridge circuitand an illustration of the physical means for vaccepting and rejectingthe Figure 2 shows one embodiment ofmy bridge circuit in-which lI employone stage amplification.

y Figure-4 illustrates diagrammatically the use of 4an indicator in theanode circuit of the amplifying-.tubeofthe one stage amplliier'shown inFigure-2 or in the anode circuit in the amplifier in thesecond stageshownin Figure 3. Figure 5-shows one arrangement for-use of a pluralityof phototubes for making moreA than one inspection.; y j Y Y Figure 6shows specifically-oneV application of the bridge-:circuitshown/infFigure 5-by l which both theY diameter and-length -ofeanarticle may berietermined..-l Y Y Y Throughoutthe-descriptionof the,drawings, the same numbers will be used for comparable parts inorderzto.` make. the drawings easierto follow. C

.Referring toEigure..1, i indicates a sourcesof lightWhichmaybefanincandescentbulb forl providing a concentrated :sourceof light althoughany other suitable sourcemay beused.` Condensinglens assembly `2 ispositioned .adjacent bulb l to Adirect a lconcentrated .light upon thespecimen 3. to.` be` tested, `said bulb.:` being preferably, .but not`necessarilyon:the opticalwaxis. oi lenses 2. A projection lens 4 ispreferably? positioned to. have its optical axis in alignment with the.`optical axisofthe condensinglenswZ-andis positioned upon the opposite.side ofthek specimen 3. from thecondensing lens tocreceive light`passing through the `inspection zonel and passing specimen 3. .A t

My invention. -hasfmanyuses in rapid, precision measurementauand. Iwillxillustrate my. invention in connection `with thejsizing ofarticlesY or specimens. My invention is adaptedto bev employed for theselecting or rejectingof .articles oi manufacture on thebasis of sizeorvdimension Vandin order to. accomplish this end, the. articles ofmanufacture or specimen areA preferably `positioned inthe light.beambetvveen the: condensing lens 2- andthe projectionslens 4 so as tointercept a portion of t-helight beam. The V block 5i or lother suitable`meanswis usedy for orienting the specimen in the photoelectric`inspection zone.

'For convenience,` the specimenis illustrated as a condensing Ulens.zand. preferably disposed. with its optical axis substantiallycoincident to the optical axis of lens 2. On the opticalaxes of thelenses described, is the magnifying mirror `6 shown as a cylinder `butother types of4 magnifying mirrors maybe used, such as afspherical `orcylindrical segment, concavo-convex, concave,

etc.` `A pair of light sensitive devices T and 8 are positioned adjacentthe projection lens `#alone on 'each side ofthe optical axis ofthe lenssystem.

Although I'have shown thellight-sensitive device l and-8 as phototubes,`any light sensitive `device including photocells `and the like-may `beused.

'i The preferred arrangement is such that the specimen 3 to be testedand the mirror 6 are positionedat the conjugate foci of the projectionlens so that a sharply defined shadow of4 thetupper edge of specimen 3is projected upon -ithe `surface of the mirror 6. Depending upon theinterception of light by the specimen, bothmay be in light or one may bein shadowfand thefother in lightsothat avery small displacementofrtheshadow'on the mirror causes a `change from one of these conditions totheotherl It can readily be seen that the spacingofgthe tubes'l and8 fromthe optical axis of the lens system determines the extreme ranges ofthediameter of the specimen, that is these distances are employed todesignate thetolerance of a substantially perfect `specimen with`respectto aperfect specimen. It

can also be seen that-if the diameterof the specimen exceeds. theupperlimit of tolerance,. both f current through-jthefamplier Ii8,`

be any `suitable kamplifying tube and :may

iinumsizeds desired, tube 1 ismovedtoward the.

optical axis. `li a greater tolerance ionamin,.- imum size is desired;tube 1f. ismoved awaywfrom the.: optical axis. Intl-1e samemanner, .thetolerance: for. the maximum size `may bey varied-'Thy moving tube. 8iwith` respect tothe optical axis` or in :respecttofthevmagnifying.mirror.` f .Shibstantially` any,.degree` of magnicatiom maybe obtained by moving the mirror 6 towardslor away from `the tubes. T.and!! Whileaat the `saine timeadjusting .the position `of'xtheprojectionllens 4 tomaintain the systemin focus; alternatively,thertubesu'! and 8 .may` be :moved toward or away from the.y mirror itLikewise, substantially any tolerance may beestablished.bytheproperspace ing of the tubes 'l andi 8 from eachfotheror from theoptical. axis ofr therlens system and av sharp cut-.oil maybe obtained `at thewextremities ofthe rangel Stillureferring to `Figure1, ameansisnshown `forremoving the varticle from theinspecton zone atthe. cud. of.` thex inspection, in` accordancaulith .whether 'thespecimen should. be accepted" or rejected. For this .purposesolenoidzvalues, vmand mi are provided. to contrer` iets. ofshigh-pressure gas,preferably air, to remo-vea specimen from the. :testingY `Zon-e. at.:the end. of` the inspection. Valves. is actuated when the `specimenshrouldabe accepted as when tube 'l is` inl shadow? and tube Bris-inlight..` Valve` t0 rejectsthe:specimen when tubes `landt are both` in.light or both in.: shadow.

VIfstubefi isdn` shadowiand `tube l. is in lightrmeans .are provided forpreventing `acceptance of:1v the specimen.

Figure 2. illustrateslthe use. of my bridgecir- `cuit in connection.with the apparatus shown in `Figure l.

Phototubes Il and 8 :andgresistors hl and` I.21form the leur` arms ofabridge connected 1 across 4a source of: direct `currentAhavingitspositive terminal at I3 andits negative terminal atilf, Thebridge .isi groundedfat l5. In Figure 2, Ihayeillustratedionly one stageamplification. :It

is lnecessary in order :to accomplishthe objects Coffmy; invention .toihave tube 8, the tube which ylis in-lightiwhen the. specimen. is. good,connected vactuatey s the energy translation means,` aswillgbehereinafter described; The `midpoint [6.0i the bridge. Lis iconnectedrto the control grid I'r'l .of the electronic tube |148rinorder-to control the flowrof The tube. |18

`vcltagefor the.v tube. |18, is further provided `by vtherdividingresistors 22, `23, 24.

A connection iamovided4 across a bridge through the. `resist-orfuconected totheA control.` grid If'I at; point/26 =`v and.; to.V the.`ground 2l. The. 1 cathodefcirtuit; .0f

tubewll is connected by means' of a slidable contactor 21-to theresistor 24 in orderlthat-the .bias on the vtube maybe properlyadjusted.A A suitable energy translation means. 28 shown as a relay coilis positioned in the anode circuit of the tube I8 and is energized oractuated only when current flows through tube I8 and is preferablyarranged so that it is only actuated when a maximum current flowsthrough I8 vin order to provide the sensitivity required for precisionphotoelectric inspections of this type.

Element 28 is shown as a conventional `relay coil, although other typesofenergy translation means may be used.` After the .tube I8 is placed incondition for conducting a current, current flows through the tube b-ymeans: ofthe power source 29 although as previously described', theoperating voltages may beprovided bythe source of D. C. potentialhavingits positive terminal at I9. The relay coil v28 is in position toactuate a vrelay switch 39 which is shown in the open position therebyclosing the reject circuit 3| con-- nected to the power source 29. Whencurrent iiows through the tube I8, .the energy translation device 28` orrelay coil is energized which actuates relay switch 30 and closes thecircuit 32 used for accepting the article which is also connected to aconventional power source 29.

It should be noted that, according to the principles' of my invention,the reject circuit is nor- 'mally'closed and the accept circuit cannotbe closed until some positive operating action occurs which insuresrthatno bad specimen will mix with thev good specimens which is vital inprecision dimensional inspections wherein the specimen may be `used inconnection with operations and devices which are Vinherently dangerousor extremely critical in such use. It is not enough .that most of thearticles sent to the accept re- `ceptacle Vare good but it is of theutmost importance that all the articles sent to the accept recepaclemeet the required specifications. If some of the good specimens are sentto the reject rreceptacle, it only means that those articles will havetobe. re-classied or that some good specifmens will bewasted, but itwould not, thereby,

effect the operation of machines in which the specimen is to be used.

Referring to Figures l and 2, in one .typical operation of my device,the specimen 3 is positi-oned in a test block 5 and if the specimen isthermore, if the tube I should 'be placed in light nand the tube 8 inshadow, a still greater negative potential is placed upon the controlgrid I'I which further'prevents tube I8 from conducting a current. Thus,it is readily seen that the only time the energy translation means 28can be actuated iswhen tube 8 receives the full light from the lightsource and tube 'I is sharply placed in Vshadow.

The'unbalancing of the bridge in the directiony .of positive potentialin order to drive the bias on the control grid Il in a positivedirection causes "current in 4tube I8 to change from substantially vnocurrent to substantially maximum current fwhich' providesthc Ipropersensitivity and speed.l

-III

required in precision measurements. I have referred herein todimensional measurementsby which I mean sizing measurements of all kinds-as well as determining shapes, angles,'bevels, location ofvslots,openings, etc.

Referring again to Figures 1 and 2 the solenoid valves 9 and vI0 may berespectively connected to the acceptV circuit. 32 and reject circuit .3|`.in order to provide a means for selecting the specimen according tothe predetermined desired inspection. y v y 1 Referring to Figure 3, Ihave illustratedthe use of the broad principle o-f my invention whereinit is desired to use two stage amplification which has particular use insome types of inspection, particularly in photoelectric inspectionswherein instead of using mechanical reference points such as the V block5 of Figure 1, the reference point is established photoelectrically.

In Figure, the position of the phototubes I and 8 in the bridge circuit.33 is reversed. Tube I which must be in shadow when the piece is good,is connected inthe positive arm of the bridge and tube 8, thetube thatmust be in light when the specimen is good, is connected in the negativearm of the bridge otherwise, the bridge is connected in the same mannerasof Figure 2. Likewise, the tube I8 is provided with its operatingvoltage and current in the same manner as that illustrated and describedfor Figure 2 with exception that means are provided for causing flow ofmaximum current flow through the tube i8 when the bridge is balanced orunbalanced to cause rejection of the article. This is accomplished Abyconnecting the control grid I'I to point 34 betweenl resistors 23 and 24and by adjusting the slidable contactor 2l on the resistor 24 the biason the tube I8 is maintained suffi'- ciently positive for the tube toconduct its maximum current.` In this. case, the tube I8 is preventedfrom conducting only under one state of light and shadow for the tubesV'i and Band that is when tube] isv in shadow and tube S is in light.Under these-conditions the bias on tube Il` is driven in a negativedirection which Asubstantially stops the flow of current to the tube I3.After the bridge is balanced due to both tubes 'I and 8 being in. lightor both being inshadow, tube I8 conducts the maximum current, or if tube'I is in light and tube 8 is in shadow, vtube l being connected to thepositive side of the bridge 33, the potential on the control grid II oftube `I8 is driven further in a positive direction thereby not effectingthe ow of current to-,the tube I8.

The anode circuit of tube I8 is connected to a direct currentsourceofvipotential at point I9 to which lineY is also connected theloadresistor 35. The second stagewamplier 36. is `shown as va gas-filled arcdischarge type of tube although other suitable types may be used. Thecathode circuit of the tube` 36 is connected between the dividingresistor 31 and 38 connected between ground 49 and the source` of D VC.potential at I9. The control grid 4I of thetube 36 .is connected to theendof the resistor 35 nearest the anode-of tube I8, in orderthat whenthe maximum current flows through the tube I8 load resistor 35 places asuiciently high negative potential on the tube 36 compared with thepotential on the cathode circuit that'the` tube 36l conductingAsubstantially no current and the. energy translation means 28 is, notactuated. WhenV tube I8 is rendered non-conducting `by' the tube 'IVbeing in shadow and tube in light, no current vv flows through tube I8and thel potentialon thefcontrol grid 41 of the `tubeiiis substantiallythat.; of g. the positive terminal t9 'of the ysource of thedirectcurrent.` Thus for the energy translation-meansltc be actuated when the'piece `-is good, the bridge` 33 isunbalancedn a: negative directioniotpotential which .prevents current from iiowing through tube I8 andpermits current to flow 'through tube 3G.

If the tube 3Bisfa `gas filled tube, it willcontinue to conduct afterbeing activated when receiving its operating voltagesiand current from adirect current source of. potential. In such a oase, a circuit breakingswitch such. as the switch, iti should be placedin` the 4anodecircuitandeither manually operated 4or mechanically. operated, beingsynchronized with the inspection operation so as to deactivate the tubeStarter-teachinspectionto prepare it` for the next-inspection. However,ifv the source of power 29 is anz alternating current, this needinot bedone fsince when the current changes` direction across the tube 3B thecontrol grid` 4l, if ata potential` suiiciently negative, willdeactivate thevtube. Theiparticular manner for deactivating* the tube:betweenin spections is not` essential` tio,4 this invention and any ofthe well `known conventional means `may be used.

Thus;within the broad principles; of my invention;` there is only onestate ofulight and shadow for the'light sensitive devices connected inthebridge circuit. 33 whichwill positively actuate the energytranslation means 28. All other states of light and shadow` of` thelight sensitive devices prevent the actuation of the energy translationmeans 28; Inl other words, theI energy translation means 281 is onlyactuated whenl the bridge circuit 33 is unbalanced in ay negative.- direction of potential. If itv is unbalanced in a positive direction.-of--potentia-l or if itis-in balance;V the energyltranslation means 28is prevented from` being actuated.

.i A selecting circuit42 isvshowngernbodying the solenoid rejecting,valve "band` the solenoid ac;- cepting valve 9 which` are connected toasource alternating current. The. relay vswitch 36 is shown in thee openposition corresponding to` the time whenzthe energy translation meansv28 is not energizeminorder` that the specimen will` pass ,tof thereject'receptacle,.unlessL some positive action occurs` to. actuateswitch 30 and` complete` the accepti eircuitl.. The: realycoil 28islactuated i.

whenthe lpiece is, good5 actuating. thef solenoid valve` il whichaccepts.. the article-.meeting the `required specifications. i p

f" In orderl toiprevent the` continuous flow: of air through the rejectside of the: V` loloclcfcam` 43 is` provided .which .only closes. the.circuit connected to the A. @current operating the solenoid valves 9and` Ill,I when the specimen` 8*isin proper test'.` position and this'isaccomplished by 'cor- -relating theA camA d3 `with means -for feedingthe specimens into test zonepr into fthe v blcckiS;

lthe potential `oni the control' grid' 1H of the tube 361wo`uldbedriven: in aipositiv direction which lwould cause current 'to flowthrough the amplifyiigtube 36 and therelay coil `28fwo'uldbe actuated;Toiprevent this; V.Il connect: the heating element. Moi the `tube I8;said element having energy supplied y bythe` Ai; (Di-.transiormer p 45;rin

series witha relay coil4 Q6. If the heating element isgood, therelaycoil 46is energized-which maintainsthe relay switch 41 inclosedposition thus maintaining the completion of the anode `circuit of thetube 36, but if the heating velerrient 44 should burnout, the relayswitch ,41 will open which breaks the anode` circuit of the tube 36thereby preventing the relay coil 23 from being actuatedwhich willinsurethat under this faulty condition; no` badpiece` will` be mixedwith the goodpieces; i Figure .4` illustrates the use of1 anindicatorvin the anode circuitpof` the tube `I8 or of the tube 36iplace of therelaycoiLsaid indicator being actuated` only whentthe `piece l-is good.`This is useful wherein accurate 1precision measurements Awill berequired by which the=sorting can be' don'e by anr operator Watching theindicator. Inother words, any means for translatingA the energy suppliedby the aimlification into the results of the inspection may be usedwithin the scope of my invention. p p.

Figure -illustrates the preferred use of aplu rality. of phototubes in abridge circuit when used in connection withmfaking two ormoreinspectionsl of the specimenV and is particularly useful inmakingtwoo-r more inspections ofthe speci.'- men andespecially in makingtwo or more ,dimen'sional inspections. In general, the bridge circuity33 in` Figure 5` isythe same as .the bridge circuit 33` illustrated inFigure 2. ,l

Referring toFiguref, the specimen 3 shown inv block 5 against the stop52 `is shown in testing position suchthatthe tubes. 118J and 5lVrneasvurethelength of. the specimen and tubes 4S `'and lillimeasure thewidth or diameter of .the specimen,

irl-.which case, for a near perfect ora perfect "speoii4 i men, thetubes 48 andm48"are inlight andthe "tubes, 5i! and i 5 l" are in shadow.The phototubs may be arranged Iinan optical system such; as that shownin Eigure i Y f ,l

Referring again to Figure 5, I have arranged .the tubes tend te, whichmust be in iight torgan acceptable specimen, `connected in. series inthepositive arrnof the bridge. `The tubes `5.0 and 5l,.,which are in shadowfor an acceptable. specimen Iare connectedfin parallel in the mega tivesideV of the` bridge. `This arrangement only ,usedinconnectionwith theillustration of Figure 2 where one stage amplification is employed.

-Thusbythis `arrangement ofthe tubes, if either of. the..i',1`1b`es`` 48or 49`are inA shadow dueto an imperfect specimen,.it opens the positiveside fof thebrideand the bridge is1unbalancedin a. negative direction ofpotential thus preventing actuationof thefenergy translation means '.28or if the tubes` 53 and` 5l areboth inshadow and` either Vthe tubes 48and 49 were inshadow, the bridge `would be4 in balance which would 4alsoprevent the actuation of the energy `translation meansA 2B. y On theother hand, by properlyadjusting the biasfon` the tube I8 through the`slidable contactor 'Zliif tubes 48 and 49 are in light and either of thetubes 50 are in light, the bridge is balanced which will indicate thatthe specimen is ^not acceptable.. Thusto.avoid all balancing `and`fJlsetting eiects in simultaneously making two or more inspections, Iprovide` ameans which will insure. the acceptance ofthe article only ifthe proper tubes'are placed in light and shadow. I wouldnotaocomplishthe objects of my invention -if Iconnected tubes land 49 in`parallel and tubesiill and 5| in series or in any other combinationothex-.thanlthe oneIhave shown in Figure 5. i Referringto Figure 5, if Iemploy a. two1 stage amplification, I connect tubes 48 and 49 in seriesin the negative side of the bridge and the tubes andinia the positiveside of the bridge 1n order to correspond to the bridge circuit 33illustrated in Figure 3. v

1 Throughout the specication Where I have referred to a positivepotential on a control grid, I mean apotential which may be slightlynegative with respect to the cathode depending on the operatingcharacteristics of the tube, but in all cases, I mean at least apotential or bias sufficient to initiate conductance of the electronictube or electronic circuit. Some tubes depending on their operatingcharacteristics will begin to conduct when the bias is within about aminus live volts.

The above described and illustrations of the drawings are not intendedto limit the scope of my invention which is only limited by thefollowing claims.

I claim as my invention: v

, 1. In a photoelectric sizing device 'for making precision dimensionalinspections of articles a source of light, a condensing lens positionedto concentrate a beam of light in an inspection zone, light sensitivedevices positioned about a magnifying mirror, at least one of said lightsensitive devices positioned to be placed in shadow andat least oneother of the light sensitive device positioned to be placed in lightwhen lthe article being tested is of a proper size, a bridge circuitincluding said Ylight sensitivedevices having the light sensitivedevices which are in light when :the article is of the proper sizeplaced in the positive arm of said bridge and having the light sensitivedevices which are in shadow when the article is of the proper sizeplaced lin the negative arm of the bridge, means for maintaining thebridge in balance when all the lightsensitive devices are in shadow orall in light, means ,for unbalancing the bridge when a portion of thelight sensitive devices are in light and another portion are in shadow,av selecting means for accepting or rejecting thel article, meansoperating` to accept the-article only when allof the light sensitivedevices in the positive arm of said bridge are in light and all of thelight sensitive devices in negative arm of said bridge are in shadow,

means operating to reject the article when the .bridge is in balance orwhen thel bridge is unbalanced in any other manner than the state ofunbalancc required for accepting the article, and means for varying thetolerance within which `the selecting means will accept the articleincluding independent means for varying the maximum tolerance and theminimum tolerance by adjustingthe .position of the light sensitivedevices .about the Amagnifying mirror.

' 2. In a photoelectric sizing device for making precision dimensionalinspectionsV of articles a source of. lightgan `inspection zone; meansfor directing abeam of light from said light source to said inspectionzone; means for positioning the article to be tested in the inspectionzone; a plurality of light sensitive devices positioned to receive lightfrom said beam, at least one of said light sensitive devices positionedrelative to said `inspection zone and said light beam so `as to beplaced in shadow and at least one other of the ,light sensitive devicespositioned relative to said inspection zone .and said light beam so asto receive light from said beam when an article of proper size is in theinspection zoneia bridge cir- .cuit including saidlight sensitivedevices havmg al1 the light sensitive devices which are in lightl whenanarticle of proper size is in the inspection zone, in one arm ofthebridge and having all of the light sensitive devices which are inshadowwhen an article of the proper size is in the inspection zone", inthe' other arm 'ofthe bridge; said bridge thereby being unbalanced inone direction of potential when an article. of proper size is in theinspection zone; means responsive to said bridge for determining theacceptance of the article only when said bridge is so unbalanced andmeans for preventing thev actuation of said acceptance determiningmeans-for all conditions of light and shadow on said light sensitivedevices other than said conditions of lightl and shadow when an articleof propersize is in the inspection zone.

3. In a photoelectric sizing device for making precision dimensionalinspections 'of articles a source of light; an inspection zone; meansfor directing a beam of light from said light source to said inspectionzone; means for positioning the article to be tested in the inspectionzone;l a plurality of light sensitive devices positioned to receivelight'from said beam, at least'one of -said light sensitivedevices'positioned relative to said inspection zone and said light beamso as to be placed in shadowV and at least one other'of the lightsensitive devices positioned relative to said inspectiori'zone and saidlight beam so as to receive light from saidv beam when an article ofproper size is in the inspection zone; `abridge circuit including saidlight sensitive devices having all the light sensitive devices whicharein light when an article of proper size is in the inspection zone, inone arm of the bridge and having all 'of the light sensitive deviceswhich are in shadow when an article of the proper size is in theinspection zone, in the other arm ofthe bridge; said bridge therebybeing unbalanced in one direction of potential when an article of propersize is in the inspection zone; means responsive to said bridge vfordetermining the acceptance of the article only whensaid bridge is sounbalanced, means for preventing the actuation of said acceptancedetermining means forall conditions of light and shadow on said lightsensitiveidevices other than said conditions of light and shadow when anarticle of proper size is in the inspection zone, and means for varyingthe tolerance within which the acceptance determining means'v isactuated including independent means for varying the maximumtolerance'and the minimum tolerance by adjusting thel position of thelight sensitive devices relative to said inspection zone and said lightbeam.

4.' In a photoelectric sizing device for making precision dimensionalinspections loi' articles a 'source `of light; an inspection zone; meansfor diceive 'light from said beam when an article of `.proper size is inthe inspection zone; a bridge circuit including said lightsensitivedevices having `all the light sensitive devices which are lin light whenan articleofproper size is in the 'inspection zone, in the negative armof the bridge and having all of theligh't sensitive devices whichare-1in shadow when an article of the proper size 1s in the inspectionzone, in the positive arm of the bridge; said bridge thereby beingunbalanced in a. negative direction of potential when an article ofproper size is in the inspection zone; means responsive to said bridgefordetermining the acceptance of the article only when said bridge is sounbalanced and means for preventing the actuation of said acceptancedetermining means for all conditions of light and shadowl on said lightsensitive devices other than said conditions of light and shadow when anarticle of ,proper size is in the inspection zone.

5. In a photoelectric sizing device for making precision dimensionalinspections of articles a source of light; an inspection zone; means fordirecting a beam of light from said light source to said inspectionzone; means for positioning the article to be tested in the inspectionzone; a plurality of light sensitive devices positioned to receivelightfrom said beam, at least one of said light sensitive devices positionedrelative to said inspection zone and said light beam so as to be placedin shadow and at least one other of the light sensitive devicespositioned relative to said inspection zone and said light beam so as toreceive light from said beam when an article of |proper size is in theinspection zone; a bridge circuit including said light sensitive deviceshaving all the light sensitive devices which are in light when anarticle of proper size is in the inspection zone,

. in the positive arm of the bridge and having all spection zone, in thenegative arm of the bridge;

said bridge thereby being unbalanced in a posi- REFERENCES CITED Thefollowing references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,722,751 Jones July 30, 19291,922,188 Zworykin 1 Aug. 15, 1933 2,033,645 Parkhill Mar. 10, 19362,065,758 Shepard, JR Dec. 29, 1936 2,085,671 Powers June 29, 19372,102,664 Alexander Dec. 21, 1937 2,114,867 Wilson Apr. 19, 19382,140,355 Gulliksen Dec. 13, 1938 2,171,362 Gulliksen Aug. 29, 19392,177,133 Desch Oct. 24, 1939 2,193,590 Gulliksen Mar. 12, 19402,298,466 Cooley Oct. 13, 1942 2,310,342 Artzt Feb. 9, 1943 pages395-397; published by McGraw-Hill Book Co., New York, 1937.

